1993 R129 300sl transmission slips off the line

[Benz Mondi]

I'm hoping I get some good new from you guys...

for about a month now, when I come to a complete stop and then attempt to accelerate in a normal way, my car will creep along (less than a walking pace) as the rev's build to about 1,800 rpm in about 4-5 seconds. Then I feel it klick (not a jolt) into the next gear and then it goes just fine the rest of the way until I have to come to a complete stop.

I changed both the fluid and the filter last week and found nothing abnormal in the fluid or the filter. No unusual noises anywhere. My car doesn't leak any fluids. No warning lights or smells. It has 117K miles on this tranny.

Perhpas related, I have to always let the car warm up for 5 mins (winter or 100 degree summer) in order for it to not stay in a lower gear as I drive down the street.

What's happening?
What kind of repairs am I looking at?
Does the tranny have to be removed for the repairs?
Just in case, anyone have a deal on a used tranny?

thanx,
Al